Field of the Invention
The invention relates to a data writing method and more particularly relates to a writing method for a resistive memory apparatus.
Description of Related Art
A non-volatile memory can retain the data stored therein even when the power is off, and therefore has become an essential memory element for the normal operation of various electronic products. Resistive random access memory (RRAM) is a type of the non-volatile memory that manufacturers in this field are zealous to develop, which has advantages, such as low operation voltage for writing, short writing/erasing time, long memory time, non-destructive reading, multi-state memory, simple structure, and small area, and has great potential to be applied to personal computers and electronic equipment.
For the resistive memory, generally, the width of the filament path may be changed by the pulse voltage applied and the polarity. Thereby, the resistance value is set to a low resistance state (LRS) or a high resistance state (HRS) in a reversible and non-volatile way for respectively representing the stored data of different logic levels. For example, a RESET pulse may be applied to narrow the width of the filament path to form the high resistance state when the data logic 1 is written. In addition, a SET pulse having the opposite polarity may be applied to increase the width of the filament path to form the low resistance state when the data logic 0 is written. Accordingly, during data reading, the data of logic 1 or logic 0 may be read according to the read currents with different ranges that are generated under different resistance states.
However, the filament path in the variable resistance element may be affected by the high-temperature environment and become unstable, which challenges the data retention of the variable resistance element. More specifically, the low resistance state may have an increasing resistance value due to the high-temperature environment and the high resistance state may have a decreasing resistance value due to the high-temperature environment. In such a situation, the ranges of the read currents respectively corresponding to the two resistance states may overlap each other. Consequently, during the data reading, the stored data of different logic levels may generate the same read current and cause the stored data to be read incorrectly.